Rotor/Drum Imbalance. Chevrolet PJJ 2001

For 1990-2009 cars

Rotors and drums do not have a set tolerance. However, rotors or drums with more than 21 g (0.75 ounce) imbalance have the potential to cause vibration. Inspect the rotors and the drums for imbalance using either the on-vehicle or the off-vehicle method.

### Checking Rotor/Drum Imbalance (On-Vehicle)

1. Support the vehicle rear axle on a suitable hoist. Refer toLifting and Jacking the Vehicle in General Information.
2. Remove the rear tire and wheel assemblies. Refer to Tire and Wheel Removal and Installation in Tires and Wheels.
3. Reinstall the wheel nuts in order to retain the rotors/drums.
4. Run the vehicle at the complaint speed while inspecting for the vibration.
5. If the vibration still exists, perform the following steps:

5.1. | Remove the rotors/drums.

5.2. | Run the vehicle back to speed.

6. If the vibration is eliminated, perform the following steps:

6.1. | Remove the rotors/drums one at a time.

6.2. | Perform the vibration test for each rotor/drum.

6.3. | Replace the rotor/drum that is causing the imbalance.

6.4. | Inspect the balance of the new rotor/drum.

### Checking Rotor/Drum Imbalance (Off-Vehicle)

1. Measure the diameter and the width of the rotor/drum.
2. Mount the rotor/drum on a balancer in the same manner as a wheel.

Important: You can only inspect the rotors/drums for static imbalance. Ignore the dynamic imbalance reading.

3. Inspect for static imbalance.
4. If the rotor/drum shows imbalance, replace the rotor/drum.
5. Inspect the balance of the new rotor/drum before you install the rotor/drum on the vehicle.